//! Forward fence, the frontend-globals ratchet.
//!
//! The legacy `static/*.js` files register behavior as `window.<name> = fn`
//! globals (the pre-module `data-action` dispatcher pattern). The frontend
//! restructure (`_private/docs/mnw/frontend/`) migrates these into typed ES
//! modules under `frontend/src`. This seal keeps the count monotonically
//! non-increasing: adding a new `window.*` global fails the build, and every
//! migrated file must lower `HIGH_WATER`. Same idea as the migration
//! HIGH_WATER seal.
//!
//! When you remove globals, lower `HIGH_WATER` to the new count (the failure
//! message reports it). Never raise it.

use std::fs;

/// Ratchets down only, never up. 115 at the start of the restructure
/// (2026-07-07); 113 after Phase 1 retired `mnw.js` (its 2 `window.*` globals
/// moved into the typed core module's bridge).
const HIGH_WATER: usize = 113;

/// Count `window.<ident> =` assignments (not `==`/`===` comparisons) across the
/// legacy `static/*.js` files.
fn count_window_globals() -> usize {
    // `=[^=]` matches an assignment `=` while excluding the first `=` of a
    // comparison operator. The regex crate has no lookahead, so this is the
    // portable form.
    let re = regex::Regex::new(r"window\.[A-Za-z_][A-Za-z0-9_]*\s*=[^=]").unwrap();
    let static_dir = concat!(env!("CARGO_MANIFEST_DIR"), "/static");
    let mut total = 0;
    for entry in fs::read_dir(static_dir).expect("read static/ dir") {
        let path = entry.expect("dir entry").path();
        if path.extension().and_then(|e| e.to_str()) == Some("js") {
            let src = fs::read_to_string(&path).unwrap_or_default();
            total += re.find_iter(&src).count();
        }
    }
    total
}

#[test]
fn frontend_globals_do_not_grow() {
    let count = count_window_globals();
    assert!(
        count <= HIGH_WATER,
        "window.* global assignments in static/*.js rose to {count} (HIGH_WATER {HIGH_WATER}). \
         New frontend code must be a typed ES module in frontend/src registered through the \
         dispatcher, not a `window.*` global. If you REMOVED globals, lower HIGH_WATER to {count}."
    );
}